Probiotic supplementation affects IGF-1 and leptin levels in Nile tilapia hepatopancreatic tissue / Suplementação com probiótico afeta os níveis de IGF-1 e leptina no tecido hepatopancreático de tilápias-do-nilo

This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.(AU)

O presente trabalho teve como objetivo avaliar o efeito da cepa probiótica Lactobacillus plantarum sobre os níveis de leptina, IGF-1 e seus receptores no tecido hepatopancreático de tilápia-do-nilo (Oreochromis niloticus) e correlacionar com o desempenho zootécnico e os parâmetros microbiológicos intestinais dos peixes. Juvenis de tilápia-do-nilo (±23g) foram distribuídos em seis tanques de polietileno (45L) conectados a um sistema de recirculação, com aeração e temperatura constantes (25°C). Os peixes foram alimentados duas vezes ao dia, a 5% da biomassa do tanque, com as respectivas dietas: controle (dieta comercial sem probiótico) e suplementada com L. plantarum (1 x 108 UFC mL-1), ambas em triplicata. Após 30 dias de cultivo, os peixes alimentados com L. plantarum apresentaram maiores ganho de peso semanal, peso final e conversão alimentar, bem como maior contagem de bactérias ácido-láticas e menor contagem de bactérias patogênicas no trato intestinal das tilápias alimentadas com dieta probiótica, em comparação ao grupo controle. A intensidade da imunomarcação para os hormônios IGF-1 e leptina foi menor com a suplementação de L. plantarum do que no grupo controle, sem alterar os níveis de seus receptores. Essa redução pode implicar mudanças importantes no metabolismo e na homeostase dos peixes.(AU)

Effects of a phytogenic, alone and associated with potassium diformate, on tilapia growth, immunity, gut microbiome and resistance against francisellosis.

This work evaluated the effects of dietary supplementation of A-Live (phytogenic) either individually or in combination with Aquaform (potassium diformate, acidifier) on juvenile Nile tilapia (Oreochromis niloticus) growth performance, innate immune parameters, gut microbiome, and resistance against Francisella noatunensis subsp. orientalis challenge. Each experimental group contained 140 fishes (34.3 ± 0.33) in two 150L tanks. The experimental design consisted of five groups: a negative control; treated groups (G1, G2, G3) supplemented with different concentrations of A-Live and Aquaform in the feed; and a positive control (PC) for pathogen infection. Groups G1, G2, G3, and PC were challenged with Francisella spp. after 15 days. After infection, the mortality was significantly lower in groups G1, G2, and G3 (p < 0.01). Furthermore, these groups showed significant increase (p < 0.05) in daily weight gain, feed conversion rate, and specific growth rate. The PC group presented increase (p < 0.05) in the leukocytes and neutrophils number. Innate immunity parameters showed no difference between treatments after infection. Microbiome analysis revealed an increased number of bacteria belonging to the Vibrionaceae family after pathogen infection suggesting a secondary pathogen function of these bacteria. These results validate the beneficial effects of these products in tilapia farming.

Tadpoles fed supplemented diet with probiotic bacterium isolated from the intestinal tract of bullfrog Lithobates catesbeianus: Haematology, cell activity and electron microscopy.

The aim of this study is to select and isolate autochthonous bacteria with probiotic potential for use in a supplemented diet for bullfrog tadpoles, Lithobates catesbeianus. A total of 20 strains of lactic acid bacteria were isolated. Nine out of these were used in the following in vitro assays: antagonism against pathogenic bacteria (ANT), antimicrobial activity from extracellular compounds (MIC), tolerance to bile salts (TBS), pH reduction, protease production, sensitivity to antimicrobial tetracycline, cell viability, growth rate and doubling time. Using these data was defined an ideotype (ideal strain) based on the best results. Distances were estimated with the Mahalanobis (D2) test, and the best candidates, presenting the shortest ideotype distances, were considered to be used. The best strain was found to be Lactobacillus plantarum because it presented 10.00 ± 0.50 mm of ANT against Aeromonas hydrophila, 3.99 ± 0.01 of MIC independent of pathogenic bacteria, 85.07 ± 0.01 of TBS, 4.20 ± 0.02 of final pH, 17.67 ± 1.15 of protease production, 13.50 ± 2.00 sensitivity to antimicrobial tetracycline, 9.36 ± 0.04 of cell viability, 0.20 ± 0.00 of growth rate and 3.46 ± 0.00 doubling time. Therefore this probiotic candidate was then supplemented (2.045 ± 1.07 × 107 colony forming unities. g-1) into the diets of bullfrog tadpoles for a period of 42 days. At the end of the trial, samples of blood and intestines were collected to verify the haematological alterations and the intestinal morphology using transmission and scanning electron microscopy. Tadpoles fed the supplemented diet showed successful lactic acid bacterium colonisation, an increased number of circulating thrombocytes, monocytes, eosinophil and LG-PAS+ and also an increase in the length and density of intestinal microvilli. This study shows the feasibility of using probiotics isolated from farmed bullfrogs as a supplement in the diets of tadpoles, providing a promising alternative for modulating the health of these animals.